1. Field of the Invention
This invention relates to a temperature sensor assembly for an automatic baking machine, more particularly to a temperature sensor assembly which can detect precisely the temperature inside the oven of the automatic baking machine so as to signal the heat device of the automatic baking machine to perform an appropriate adjustment for the oven.
2. Description of the Related Art
The improvement of this invention is directed to a conventional temperature sensor assembly 10 which is installed in an automatic baking machine 1, as shown in FIG. 1. The automatic baking machine 1 includes an oven 11 with a hole 111 formed through a vertical wall thereof, and a container 12 disposed within the oven 11 so as to bake bread therein. The oven 11 has a heat device 112 mounted therein and capable of heating the container 12 according to the signal generated by the temperature sensor assembly 10.
Referring to FIGS. 2 and 3, the temperature sensor assembly 10 includes a hollow receiving unit 101, a positioning member 102, a U-shaped insulated sleeve 103, a sensor member 104, and a shell member 105.
The receiving unit 101 includes a positioning plate 1011 which is connected threadably to the vertical wall of the oven 11 (see FIG. 1), and a housing 1012 which is mounted securely on the positioning plate 1011 and which has an opening in alignment with the hole 111 of the oven 11 (see FIG. 1). An elongated passage 106 is communicated with the housing 1012 of the receiving unit 101 so as to allow a pair of conducting wires 113 to extend therethrough. The conducting wires 113 are adapted to connect electrically with a control system (not shown) of the automatic baking machine 1 so as to actuate the heating device 112 in order to heat the container 12 (see FIG. 1) when the temperature inside the container 12 is below a predetermined temperature.
The positioning member 102 includes a block 1021 which is located in the housing 1012 and which has a notch 1022 (as best shown in FIG. 4) formed in a surface thereof, and a pair of lugs 1023 which respectively project outward from the intermediate sections of the opposite side walls of the block 1021. The notch 1022 has a semicircular cross-sectional surface so as to hold the intermediate portion of the insulated sleeve 103 in the notch 1022 (as shown in FIG. 4). Each of lugs 1023 has a positioning hole 1024 formed therethrough so as to allow two end portions of the insulated sleeve 103 to extend respectively through the positioning holes 1024 of the lugs 1023, thereby positioning the insulated sleeve 103 on the positioning member 102.
The sensor element 104 includes a cylindrical sensing portion 1041 which is inserted fittingly into the intermediate portion of the insulated sleeve 103, and two conducting legs 1042 which extend respectively through the end portions of the insulated sleeve 103 and which are connected respectively and electrically to the conducting wires 113. The insulated sleeve 103 can prevent the conducting legs 1042 from contacting other conducting materials in order to maintain the precision of the sensor element 104.
The shell member 105 is coupled with the housing 1012 of the receiving unit 101 and extends through the hole 111 of the oven 11 (see FIG. 1). The shell member 105 has a heat transfer portion 1051 near the container 12 (see FIG. 1). The heat transfer portion 1051 is made of a heat-conductive material, and presses against the intermediate portion of the insulated sleeve 103 so as to position the positioning member 102 and the insulated sleeve 103 between the shell member 105 and the housing 1012. Because of its proximity to the container 12, the heat transfer portion 1051 can transmit heat inside the container 12 to the sensing portion 1041 via the intermediate portion of the insulated sleeve 103 quickly. By means of the conducting legs 1042 and the conducting wires 113, the sensing portion 1041 can signal the control system of the automatic baking machine 1 so as to actuate the heat device 112 to heat the container 12, as shown in FIG. 1.
The drawbacks of the conventional temperature sensor assembly 10 are as follows:
1. The size of each part of the sensor assembly 10 has to be designed as small as possible in order to achieve a shorter reaction time. However, when positioned on the wall of the oven 11, the block 1021 of the positioning member 102 is likely to tilt to a side wall of the shell member 105, as shown in FIG. 5. As a result, the intermediate portion of the insulated sleeve 103 deviates from its original position. This may affect the precision of the sensor element 104. PA1 2. In order to prevent the sensing portion 1041 of the sensor element 104 from being crushed as a result of the heat transfer portion 1051 of the shell member 105 pressing directly against the sensing portion 1041, the insulated sleeve 103 must be sleeved on the sensing portion 1041 of the sensor element 104. However, the insulated sleeve 103 may delay the heat transfer speed from the heat transfer portion 1051 to the sensing portion 1041 of the sensor element 104. This also affects the precision of the sensor element 104.